Contextual fear conditioning depresses infralimbic excitability

Area of Science:

• Neuroscience
• Behavioral Neuroscience
• Psychiatry

Background:

• Posttraumatic stress disorder (PTSD) is linked to hypoactive ventromedial prefrontal cortex (vmPFC) in humans, impairing context discrimination.
• Auditory fear conditioning in rodents depresses neuronal excitability in the homologous infralimbic cortex (IL).

Purpose of the Study:

• To determine if contextual information alone is sufficient to induce IL neuronal depression.
• To investigate the role of IL excitability changes in contextual fear memory.

Main Methods:

• Rats underwent contextual fear conditioning, context-alone exposure, or pseudoconditioning.
• Whole-cell current-clamp recordings were used to assess IL neuronal excitability in brain slices.
• Neuronal firing patterns and afterhyperpolarization potentials were analyzed.

Main Results:

• Contextual fear conditioning significantly reduced IL neuronal firing in response to depolarizing stimuli.
• Neurons from fear-conditioned rats exhibited increased slow afterhyperpolarization potentials (sAHPs).
• Changes in IL excitability correlated with the expression of contextual fear.

Conclusions:

• Contextual fear conditioning, independent of specific cues, depresses IL neuronal excitability.
• IL neuronal depression and altered sAHPs may contribute to the neural mechanisms underlying contextual fear encoding.
• Findings suggest IL dysfunction could be a target for PTSD interventions.